Color Head to Head Consistency for VC Printing?
I have a two part question that relates to printing on VC paper using subractive color heads.
These color heads have YELLOW, MAGENTA, and CYAN filters that can be inserted into the white light stream in varying degrees from "0" to "200" color units. At least, that's the range of color units on my Beseler 45s.
How consistent are these color units from one head to another? If I change heads, or even brands of heads, can I expect to obtain the same printing color of light (i.e. the same paper contrast) by dialing in the same color units on the new head as on the previous head?
I keep good notes on how I print a given negative. I want to reproduce the same print later and have it look like the print I used to write the notes.
Does it make sense to use a color analyzer and record the color for a given negative, and for future reference in that regard? So, if one changes a head or brand, then in theory, one could always get back to the original color with a different enlarger head?
I ask these questions, because I've not used a color head for VC printing, and I've not used a color analyzer.
They are not very consistent from the few I've used. The color analyzer sounds like a good idea, but I haven't tried it.
Maybe you would be best served by using a step wedge and figuring out what the real grade is at your common filter values. Then you could do the same on the new enlarger. I use an RH Designs analyser and it works on true contrast grades if you take the time to profile it. So with it I can switch papers easily. Switching light sources would be equally easy except I have one specific to my Ilford head.
Filters can fade a bit over time. The light boxes yellow. Bulbs age. A new Kodak standard head should be fairly close to a new Kodak head from a different maker [The US companies use Kodak standard. Durst uses it's own which is slightly different]
Not sure how much or even how exactly you'd use a colour analyzer for this. Really all it should take is a few test prints with the new head. Plus B&W is less sensitive I think then colour printing. So I'm not sure how many people would notice if you're settings were 10 points off. Really if you've got grade 2.6 instead of 2.55 how many will notice?
The dichroic filter in the heads are pretty stable, though their values may differ from model to model. I have two Chromega D color heads. One came with the enlarger, and the other I picked up at a fire sale. At first they did not match up at all, and I was scratching my head trying to figure out why. So I lit them up side by side looking for color temperature differences. It was obvious upon comparing them side by side, that one was very yellowed with age. Opening up the light mixing chamber revealed that the reflective lining had indeed yellowed after years of exposure to the high intensity halogen lamp. After refitting the yellowed lightbox with new reflectors, they matched up pretty closely. I'll bet that if I changed the lamps and the IR filters out with brand new parts they'd be even closer. As it is, I don't bother. It's not like I'm going to be swapping heads for no reason other than to say I did it.
I second this approach! This is the only way to do it. Calibrate your enlarger to ISO grades, record your printing data in ISO grades and f/stop timing, and if you move to another setup, calibrate this new setup to ISO grades again, then use your records to print with amazing consistency.
Originally Posted by L Gebhardt
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Assuming your color analyzer is stable, I think that's your best approach. But then, no one has mentioned how much variation there is in paper, from batch to batch. I've never checked it, maybe Ralph has some ideas there.
Are you using first world manufactuered papers, or second or third world?
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I'm afraid not be be a good source for this information, because I buy paper in quantities, large enough, to last me for several years. I'm more concerned about paper aging than batch-to-batch differences.
Originally Posted by Kirk Keyes
However, I know from Howard Bond and John Sexton, them working with Ilford and Kodak papers respectively, that they found the variation to be minimal. Indeed, if I switch to 'new' Ilford paper after 2 years or so, I retest, but only find minute differences in speed or contrast. Again, has more of an effect than batch-to-batch variation does for me.
Ilford had, and hopefully still does have, an excellent quality control system.